Hearing aid microphones are electroacoustic transducers which convert acoustical energy (e.g., sound waves) into an audio signal. This signal is then processed (e.g., amplified) and sent to a receiver, which converts the processed signal into acoustical sound waves that are output toward the eardrum.
Design considerations for hearing aid microphones include, but are not limited to, size, bandwidth, and ease of repair. Minimization of the hearing aid size is an ever present aesthetic concern. Decreases in the microphone size or the microphone mounting structure enables a corresponding decrease in the size of the hearing aid. For this reason, many conventional hearing aids employ an adhesive connection (e.g., glue) to secure the microphone relative to the faceplate. However, the harsh environment faced by hearing aid microphones often necessitates repair or replacement of the microphone. Despite the size-minimization benefit provided by directly gluing the microphone to the faceplate, such hearing aid microphones are difficult, if not impossible, to repair or replace without breaking either or both of the microphone or faceplate.
Bandwidth is another design consideration. Bandwidths, previously limited to about 6-8 kHz by clock frequencies below about 16 kHz, are now required to extend up to about 10 kHz, with particular emphasis on the higher frequencies.
WO 01/54457 discloses one conventional “in the ear” (ITE) hearing aid for at least partial insertion into the ear canal comprising a housing, a faceplate 1, a battery drawer compartment 6, and a microphone 8, 9 mounted at least partially in the faceplate. As shown in FIG. 4, microphone 8, 9 is held in place by locking arms, which are not numbered. A sealing element 10 is provided to form a seal between the faceplate 1 and the microphone 8,9, and possesses openings in line with corresponding openings in the faceplate and the microphone. As microphone 8, 9 is held in place by the locking arms, sealing element 10 appears likely to be at least substantially non-adhesive, which would facilitate repair and/or replacement of the microphone.
However, the structure of the locking arms in the hearing aid of WO 01/54457 disadvantageously demands significant space both adjacent and behind the microphone 8, 9. As an initial matter, the length of the microphone is an important parameter. As shown, the locking arms limit the length of the microphone 8, 9 by an amount corresponding to the height of the inwardly projecting members of locking arms. More significantly, electrical contacts for hearing aid microphones are typically provided on the backside of the microphone, such as by a printed circuit board that is glued to the microphone housing. Any variations in the distribution of the glue can lead to overall microphone length variations which, when coupled with an attachment device that grips the rear surface of the microphone, as shown in WO 01/54457, results in uneven pressure on the sealing element 10.
Despite the improvements realized by WO 01/54457, room for further improvements to hearing aid microphones and for hearing aids incorporating such microphones to facilitate repair and/or replacement of the microphone, minimize the size of the hearing aid, and/or provide enhanced bandwidth is desired.